Chemical kinetics of the azide radical:: Rate constants for reactions with Cl, NO, NO2, O2, CO, CO2, Cl2, and C3H6

The reactions of the azide radical ((X) over bar (2)Pi(g)), produced by the reaction of F atoms with HN3, with F, Cl, NO, NO2, O-2, CO, CO2, Cl-2, and propylene have been examined in a room-temperature flow reactor. The relative concentration of N-3 was monitored under pseudo-first-order conditions using laser-induced fluorescence. A microwave discharge applied to a dilute flow of CF4 in argon served as the F atom source for the F + HN3 reaction. Using reactant concentrations of (0.5-4.0) x 10(12) and (1.0-4.0) x 10(12) molecules cm(-3) for CF4 and HN3, respectively, the rate constant for the N-3 + F reaction was found to be (4.1 +/- 0.3) x 10(-11) cm(3) molecule(-1) s(-1), which compares favorably with the accepted value of (5 +/- 2) x 10(-11) cm(3) molecule(-1) s(-1) The reaction with Cl atoms was examined using reactant concentrations of (5.5-9.4) x 10(11), (2.0-4.0) x 10(12), and (1.0-22.0) x 10(12) molecules cm(-3) for CF4, HN3, and Cl-2, respectively, and the rate constant is (2.1(-6.0)(+1.0)) x 10(-11) cm(3) molecule(-1) s(-1). The rate constants for the reactions of N-3 With NO, NO2, and CO were determined to be (2.9 +/- 0.3) x 10(-12), (1.9 +/- 0.2) x 10(-12), and (1.8 +/- 0.2) x 10(-12) cm(3) molecule(-1) s(-1) respectively. The reactions between azide radicals and Cl-2, CO2, O-2, and propylene all occur with rate constants less than 5 x 10(-13) cm(3) molecule(-1) s(-1), indicating that N-3 is not an especially reactive radical. The bimolecular self-destruction rate for azide radical was also examined. An upper bound on the rate constant was determined to be less than or equal to 1-2 x 10(-12) cm(3) molecule(-1) s(-1). The possible products and the reaction mechanisms of these reactions are discussed.